Detecting Outdated Proxy Configuration

Dear HTTP enthusiasts,

Clients relying on explicit HTTP proxies often need to frequently query
proxy configuration files (PAC files today, PvD-based proxy configurations
in the future) to detect updates. This can lead to unnecessary polling,
increased network load, and delayed application of critical changes.

To address this, I’ve published a simple draft that defines a mechanism for
proxies to inform clients when their configuration appears outdated. The
draft introduces two new HTTP headers:
- Proxy-Config: included in client requests to indicate the URL and
timestamp of the current proxy configuration.
- Proxy-Config-Stale: an optional response header used by the proxy to
signal whether the client’s configuration is outdated.

This mechanism is compatible with any HTTP and MASQUE proxying including
CONNECT, CONNECT-UDP, CONNECT-IP, and templated CONNECT-TCP. It's designed
to be lightweight, advisory, and backward-compatible.

Feedback and suggestions are very welcome.

Best Regards,
Yaroslav

---------- Forwarded message ---------
A new version of Internet-Draft
draft-rosomakho-httpbis-outdated-proxy-config-00.txt has been successfully
submitted by Yaroslav Rosomakho and posted to the
IETF repository.

Name:     draft-rosomakho-httpbis-outdated-proxy-config
Revision: 00
Title:    Detecting Outdated Proxy Configuration
Date:     2025-06-29
Group:    Individual Submission
Pages:    9
URL:
https://www.ietf.org/archive/id/draft-rosomakho-httpbis-outdated-proxy-config-00.txt
Status:
https://datatracker.ietf.org/doc/draft-rosomakho-httpbis-outdated-proxy-config/
HTML:
https://www.ietf.org/archive/id/draft-rosomakho-httpbis-outdated-proxy-config-00.html
HTMLized:
https://datatracker.ietf.org/doc/html/draft-rosomakho-httpbis-outdated-proxy-config


Abstract:

   This document defines a lightweight mechanism that allows explicit
   HTTP proxies to inform clients when their proxy configuration, such
   as a Proxy Auto-Configuration (PAC) file or Provisioning Domain (PvD)
   proxy configuration, is outdated.  Clients signal to the proxy the
   configuration URL and the timestamp of when it was last fetched.  In
   response, the proxy may indicate that a newer version of the
   configuration is available.  This enables clients to refresh their
   configuration without relying on frequent polling or short expiration
   intervals.  The mechanism is designed to be compatible with existing
   proxy deployment models and supports both PAC-based and PvD-based
   configurations.



The IETF Secretariat

-- 


This communication (including any attachments) is intended for the sole 
use of the intended recipient and may contain confidential, non-public, 
and/or privileged material. Use, distribution, or reproduction of this 
communication by unintended recipients is not authorized. If you received 
this communication in error, please immediately notify the sender and then 
delete all copies of this communication from your system.